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diyisalotoffun 06-03-2011 02:48 PM

Cantilever Fireplace?
1 Attachment(s)
I just removed our old wood burning brick fireplace and I am now getting ready to prepare for a new gas fireplace (Mendota FullView, rear vent). The fireplace was attached to the side of the house, so there is no cripple wall and the subfloor is gone where the hearth used to be. The foundation just continues along the wall (I'll try to post a picture).

The new fireplace should be flush with the inside wall, so it will 'hang' past the house wall, where the brick fireplace used to be. I was originally planning to poor a U shaped foundation that I would attach to the existing foundation using dowels. On top of that would be regular framing and enclosing of the fireplace.

I recently thought about just extending the existing joists and instead of adding a foundation, to just cantilever the small attachment that encloses the fireplace.

Does anyone have advice on what would be better?

We live in Palo Alto, CA - no snow, frost ...


diyisalotoffun 06-03-2011 02:56 PM

1 Attachment(s)
This sketch shows the attachment with the foundation as originally planned.

AndyGump 06-03-2011 05:57 PM

Your situation is a bit unusual but it looks to me like the city will require you to bring the new portion of the wall up to code.

Meaning they will want site plan, floor plan, elevations, structural details (prescriptive) and notes for California Energy Standards (Title 24).

May or may not need CF-1r, depends on how persnickety they will be.

Hey, you live in California.


diyisalotoffun 06-06-2011 12:43 PM

not really sure what you mean with unusual and it doesn't really answer my question at all, which is not about the wall, but about either doing a cantilever or building it up with a foundation.

I will look into the codes though for the wall construction.


AndyGump 06-06-2011 01:56 PM

O.K. I apologize for trying to give you my professional opinion on your entire job.

I will not make that mistake again.

Build it the way you see fit then.


diyisalotoffun 06-06-2011 02:06 PM

Andy - so what is your professional opinion then: cantilever or building on a concrete foundation?

btw, i shoudl add that I already have the permit in hand and was not asked about floor plans etc.

AndyGump 06-06-2011 02:09 PM

My professional opinion is to look at the scope of the entire job, not just one aspect and do it (at the least) code and get permits.


diyisalotoffun 06-06-2011 02:11 PM

I have the permit already.

AndyGump 06-06-2011 02:13 PM


Originally Posted by diyisalotoffun (Post 662140)
I have the permit already.

Then you must have a plan, what does it say about building it?


diyisalotoffun 06-06-2011 02:21 PM

1 Attachment(s)
the plan is what i just said above: build up structure on a u-shaped foundation. I am attaching a picture that they approved. The walls and everything will be up brought up to code. My question is if I should go back and instead of doing the foundation/framing, just ask the city to change the plan to a cantilever design which would not need the u-shaped foundation.

AfterDinner 06-06-2011 02:31 PM

I would not cantilever this. I am not sure what the weight is of your new fireplace, if heavy, definitely don't cantilever the new fireplace. If it is not heavy, cantilevering can be done, but I personally don't see the value over doing it properly. Cantilevering an existing structure is not great. If you are considering cantilevering the fireplace, why not put in posts, similar to a deck, and build on that. You could then enclose the base. Obviously, your best bet is the foundation extension, but it would be the hardest and most costly to construct.

I would definitely look into building codes for your area to make sure whatever you choose is acceptable.

diyisalotoffun 06-06-2011 02:34 PM

AfterDinner - Thanks for the advice. The fireplace is about 250lbs, but the wall including the stucco will add quite a bit to it. Sounds like it is best to stick with the original design and build a foundation.


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